Capturing Mosul is complicated because of tangled local politics, demographics and size

A rapid advance toward the Islamic State-held city of Mosul in the past few weeks has exposed tensions among competing Iraqi political factions over who will participate in the final offensive and who will govern the city if it is recaptured.

The fight for Mosul is high on the agenda this week as international defense and foreign ministers gather in Washington to discuss military strategy against Islamic State and raise funding for Iraq, where a humanitarian crisis is already unfolding among the millions displaced by the fighting....